Chapter 1: Physical Quantities and Measurements

20 Question-and-Answer flashcards covering the key learning outcomes for Chapter 1, including definitions, SI units, prefixes, measurement instruments, error types, and data-handling concepts.

What is a physical quantity?

A measurable property of matter or energy that can be expressed with a numerical magnitude and a unit.

How do physical quantities differ from non-physical quantities?

Physical quantities can be measured objectively with instruments, whereas non-physical quantities (e.g., happiness, beauty) cannot be directly measured.

What two components make up every physical quantity?

A numerical magnitude and an associated unit.

Differentiate between base and derived physical quantities.

Base quantities are independent and defined by SI units (e.g., length, mass); derived quantities are combinations of base quantities obtained through multiplication or division (e.g., velocity, density).

How many base quantities are in the SI system?

Seven.

List the seven SI base quantities with their units and symbols.

Length-metre (m); Mass-kilogram (kg); Time-second (s); Electric current-ampere (A); Thermodynamic temperature-kelvin (K); Amount of substance-mole (mol); Luminous intensity-candela (cd).

Give an example of a derived quantity and its SI unit.

Velocity (m s⁻¹) or any other such as density (kg m⁻³).

Why is scientific notation used in physics?

To express very large or very small numbers concisely and to simplify calculations.

Write 0.00052 m in scientific notation.

5.2 × 10⁻⁴ m.

What is the prefix for 10³ and its symbol?

Kilo (k).

What is the meaning and symbol for the prefix micro?

10⁻⁶, symbol µ.

State the least count of a typical laboratory metre rule.

0.1 cm (1 mm).

What is the usual least count of a vernier calliper?

0.01 cm (0.1 mm).

What is the usual least count of a micrometer screw gauge?

0.01 mm (1 × 10⁻⁵ m).

How can you measure the volume of an irregular solid using a measuring cylinder?

Submerge the object in water and record the rise in water level; the volume displaced equals the solid’s volume.

Name two instruments commonly used to measure time intervals in the lab.

Stop-clock (analog) and digital timer (or stopwatch).

What are systematic errors?

Consistent, reproducible errors caused by faulty equipment or bias that shift all measurements in the same direction.

What are random (human) errors?

Unpredictable variations in measurements due to observer limitations or environmental fluctuations.

How can random errors be reduced in an experiment?

By taking multiple readings and calculating their average.

Why are significant figures important when recording measurements?

They reflect the precision of the measuring instrument and prevent overstating accuracy.